Moor Frog

(Rana arvalis)

Facts

IUCN LEAST CONCERN (LC)

Facts about this animal

Small bulky frog, 5,5-6 cm long (up to 7 cm). Dorsal coloration grey, light-olive, brown, yellowish or rufous, during the breeding season bluish. Dark spots of 1-3 mm on dorsal and lateral surfaces varying considerably in number, arrangement and size. Light middorsal band with regular edges frequently present. “Bandid like” black marking running from the nose to the ears. Belly white or yellowish without pattern or with pallid-brownish or greyish spots on the throat and chest.

Hibernation extends from September-November to February-June, in dependence on latitude. Reproduction occurs from March-June, usually some days after the end of hibernation. Males form breeding choruses. The total duration of the breeding season within a pond is 3-28 days. Eggs are deposited in shallow, well-warmed sites, during both day and night. Spawning by the Moor Frog peaks later than that of the Common Frog. The clutch contains 500-3000 eggs deposited usually in one, rarely in two clumps. Metamorphosis occurs from the beginning of June to October in different regions. Tadpoles eat Chlorophyta, Cladocera, and other algae, higher plants, detritus, as well as small amounts of invertebrates. Recently metamorphosed froglets forage on Acarina, Collembola and other microarthropods.

Did you know?
In the dense schools of tadpoles (several hundred individuals per liter), density-dependent regulation of development takes place: The density does not influence larval survival rate directly but influences the probability of successful metamorphosis because fastly developing tadpoles often complete their transformation, while slowly developing specimens die in drying wetlands.The name Rana arvalis means “Frog of the fields”.

The Moor Frog inhabits the zones of tundra, forest tundra, forest, forest steppe, and steppe, forest edges and glades, semi-desert, swamps, meadows, fields, bush lands, gardens. It generally inhabits drier and more open sites than the Common Frog (Rana temporaria), including forest edges and glades, swamps, meadows, fields, bushlands gardens, etc. Indeed The Moor Frog is in the European region probably a more thermophilous species than the sympatric Common Frog. It frequently occurs in warmer and drier microhabitats. In Siberia, the species lives mainly in open swamps.

Wild population

Rana arvalis is one of the most abundant amphibians in central and eastern Europe, as well as West Siberia. There, its population density reaches several hundred individuals per hectare. Local density may even be higher. The species is generally neither declining, nor threatened. However in addition to anthropogenic factors leading to local declines of the species (urbanisation, recreation, tourism), industrial pollution also negatively affects populations. It leads to an increase of frequency of morphological abnormalities and disturbances in embryonic and larval development.